Which of the following groups of animals has suffered the largest percentage of known extinctions in the last 400 years?
question 18 options:

amphibians

birds

invertebrates

mammals

The correct option is d) mammals

Explanation:

Studies made by scientists have shown that mammals are nor able to evolve fast enough as compared to other groups of animals. As a result, mammals tend to become more extinct as compared to organisms of the groups. Many mass extinctions of mammal organisms have been recorded over the past 400 years. The mammalian organisms possess little biodiversity in them as compared to organisms of the other phyla.  

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.